Liberator21

I got the high flow needle and seat that I ordered from Carbs Unlimited. The new one does not have the "windows" on the sides for the fuel to flow out, so it only flows out over the top of the seat assy. This is the first time I've seen one without them. I called carbs unlimited, and when I asked why, the answer I got was "It's a different manufacturer". That's not the answer I was looking for. When I asked him about how it would flow, he said "it will be fine", in a tone that indicated he wanted me off the phone. My question is, has anyone used this one before, and how did it work? Also, I was thinking about putting the new one on the ol' Brigeport, and milling the slots myself. Would there be any advantage to adding the "windows", or am I just worrying about nothing? Check out the picture. On the left is the old one (.136"), on the right is the new one (.149").

Ted G

iTrader: (1)

I would suspect that if the windows were cut in it might make the tower weak due to the thinner walls. But maybe a few holes bored would be o.k.

blue thunder

As long as the .149 is the smallest restriction the flow will see, it will work fine. I am sure there is more than .149 area between the needle and walls of that seat. Can't see why opening it up would hurt, but don't think it will help either. As I sure you are aware, you'll need to lower the float setting when making this change to a larger needle/seat.

Dave

Liberator21

I haven't heard about lowering the float level. Why would I need to do that? If I set the float correctly with the new needle and seat, the fuel should reach the correct level, only faster. At least that's what I would think, but I'm not a carb expert.

blue thunder

Assuming fuel pressure remains the same.... with a larger needle/seat the fuel pressure has a larger area to exert force. This force is to be counteracted by the bouyancy of the float. In order for the float to counteract the increased force on the needle/seat, the float will need to be slightly further submerged. If you do not counteract this fact by lowering the float level, the resulting fuel level in the bowl with be higher. The higher fuel level will result in all sorts of ill tuned affects.

I installed .149s in two carbs last summer and had a good result. If you like I can try to research what I set them at. I am pretty sure the Dennis Moore bbc book mentions it, but I may have gotten the actual dimension out of a qjet performance tuning book which I cannot now find.

Let me know,

Dave

Liberator21

Yeah, what you say makes complete sense. Hydraulics 101, I should have realized that. If you can find the float height info that would be great, I could really use that.
My email is: [email protected]. As far as modifying the seat goes, I think I'm going to leave it alone. I went on Edelbrock's site, and their high flow seat is exactly the same. Now I'm going upstairs, grabbing a beer, and plopping my a$$ on the couch to watch American Chopper! Last time I had my bike out was new years day. Too cold now! Thanks for the info.

Paul

blue thunder

Your float setting with the .135" n/s should be .296" +/- .010" at the toe of the float. To use the .149" n/s lower the setting .045 to .251 +/- .010. That is what I set mine at and it worked well with my standard block mount fuel pumps.

Hope this helps,

Dave (Personally I am an OCC fan )

Liberator21

OK, let me make sure I'm not getting this backward. I'm lowering the float setting, right? So because your measuring from the top of the casting to the toe of the float, lowering the float would increase the distance measurement. That means if I took your .296" measurement , and lowered the float by .045", the new float measurement should be .341" as measured from the top of the casting. Is that right? A measurement of .251" would actually raise the float, again, if I took my measurement from the top of the casting. Is that correct?

blue thunder

Yep you are right liberator. I had it backwards. Here is a chart out of my HP qjet tuning book that show the progression in float level as you go up in needle size. The range it is to be lowered in 1/32 to 1/16", I just split the difference at .045. The number you figured would be correct.

Good luck,

Dave

Liberator21

Could you email that chart to me? I can't download yet.
[email protected]

Thanks